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60cm WRGB2 with a 90cm low-profile tank


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Hi guys, I am currently planning to set up a 90cm x 30cm x 30cm high-tech tank.

I am looking for light options and I currently have a Chihiros WRGB2 60cm light on hand, and I was thinking if it would be adequate for a tank of this size. I am planning to use a hanging kit to suspend the light over the middle of the tank (Side note, has anyone used the hanging kit on 6mm thick glass before?).

If I were to run it at 100% intensity, how high should the light be above the water level?

Here are the stats of the 60cm light:


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I have this exact light on my 60L (17-gal) tank, which is smaller than yours (60cm x 30cm x 36cm tall).  I have the bigger version (WRGB II 90) on my 45-gallon, which is closer to your tank size but about double the height (90cm x 30 cm x 61 cm tall).  I've run them both for about a year.  These lights are super bright - I run them between 30-40% intensity and when I was running them anywhere from 60-80% intensity I struggled with algae (hair algae in the smaller one, which has CO2, and black beard algae in the bigger one, which for most of the last year+ has not had CO2).  On the bigger tank, the WRGBII 90 is 4.5" from the water level, and on the smaller tank it hangs (using the hanging kit) 6" above water level.  It's hanging over copper pipe that I mounted to the back of my stand (which is home-made). 

I believe you'd want to mount is at least 6-8" from the water surface to get decent light spread.  I'd definitely try with the WRGBII 60 light since you already have it, and if you don't like how it looks consider investing in the WRGBII 90.  Because your tank is shallow, I think you'll be totally fine with the 60 mounted higher than mine is.  But that also depends on how particular you are about the final "look" - if you're heavy into aquascaping and the "perfect" look, then you'll want to scape with the smaller light footprint in mind (more plants in center and maybe some hardscape on the sides to bring those plants closer to the light or just direct attention towards the area with more light.  Also, I wouldn't start it at 100% intensity.  I'd start it more like 50% even if it's mounted 8" above.  Once that algae takes off it's a lot harder to control!

Here are some pics of my tanks, if that helps.  Don't mind the shoddy plant growth - I am into keeping blackwater fish but also very much into plants, so these tanks are the fragile result of my brain melting because I can't "have my cake and eat it too."  Also, the big one is quite dark because I just added fish that day - I think I set it at 6-8% intensity.

Top pic - the smaller tank with the WRGBII 60 (sorry this doesn't show the hanging mount, but I can take a photo of that tmr if it would be helpful).

Bottom pic - the bigger tank, same area as yours but twice as high, with the WRGBII 90.  This tank doesn't have a lot of stem plants in the pic (now it has none b/c I removed them) because it has a lot of floating plants to keep my Hemirhamphodons from hating each other so much.  It also gives them cover from the lights, which they are not too fond of.  However, before I added the halfbeaks (so, for 6-8 months last year) I was growing those stem plants you see without any issue with max intensity around 60%.  They looked great back then.  Keep in mind that light intensity is inversely proportional to the square of the distance from the source, and my tank is 61cm tall.  These are very bright lights!


Edited by Jess
corrected the light on my 45-gallon (WRGBII 90 not 60)
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